The invention relates generally to methods for coating objects and particularly to methods for applying flock to all of the surface of an object without leaving support marks.
Whenever a three dimensional object is supported while a coating of material is applied, there are invariably areas of the object's surface that are not coated because they were shielded by the support. The problem is not always serious. If a first coat leaves gaps in coverage the object may be supported elsewhere and a second coat may be applied to the surface area that includes the gaps. This solution is suitable if the overlap of the first coat by the second that is bound to occur does not detract from the overall appearance or function of the object. If the overlapping of coats that results from this method does detract from the appearance or function of the object, the method is obviously not suitable.
The gaps could be avoided altogether by supporting the object without physically contacting its surface. However, techniques for this, such as air cushion supports, magnetic suspensions, and electrostatic suspensions, are difficult and expensive, and not suitable or practical for many objects. The gaps can also be minimized, by using support structures such as pins that greatly reduce the area shielded from coating. For some purposes, the small gaps in the coating that result may be acceptable.
For some forms of coating, overlapping coats are not suitable, and even minimal support marks are undesirable. Flocking is an example of such a coating. In flocking, fibers are deposited by mechanical or electrostatic methods on an adhesive coated surface, the ends of the fibers being imbedded in the uncured adhesive. The adhesive is then cured or set. Since the process has two steps, and the flocking has a texture, overlapping "coats" of flocking would be unacceptable. Any gaps in flocking tend to be obvious, particularly where the flocked fibers are long, since the texture of the surface created by the flocking exaggerates the impression the gaps make. A flocked tennis ball, for example, may be produced by automatic machinery to provide an inexpensive substitute for the traditional tennis ball in which the covering is applied by hand if the flock surface can be obtained unmarred by defects caused by supports.
In my co-pending application, Ser. No. 744,941, filed Nov. 24, 1976, I have set forth a method of flocking in which I cured the adhesive in which the fibers are embedded by an electron beam of relatively low energy. It is an object of this invention to provide a method for applying coatings such as flocking to three dimensional objects without leaving unsightly support marks. It is another object to use electron beam curing to provide for applying coatings such as flocking to objects in a way that makes supporting the object during the coating process simple and secure. Other objects of the invention will be pointed out, or be inherent, in the following description of the invention.